Thymic carcinoma, a malignant thymoma, is rare in the anterior mediastinum. Typically it occurs after age 40 years, presents as an asymptomatic disorder for prolonged periods of time, and is incidentally detected by chest radiograph. Symptomatic patients often complain of a dull ache or chest pain. Cardiac tamponade as the first manifestation of these advanced thymomas is unusual. We now report the case of a 47-year-old man who experienced sudden onset syncope because of cardiac tamponade and massive pleural and pericardial effusions resulting from a huge thymic tumor. Emergency pericardiocentesis and thoracentesis terminated the life-threatening episode. The tumor and lung lesion were resected. Pathologic examination showed a moderately differentiated squamous cell carcinoma. Postoperative radiotherapy and chemotherapy were introduced. The patient has subsequently done well for the past 10 months.